CN114301361B - A control method for electrolytic capacitor-free permanent magnet synchronous motor drive system based on bus current control - Google Patents

Abstract

The invention discloses a control method of a permanent magnet synchronous motor driving system without electrolytic capacitor based on bus current control, which comprises the following steps: directly calculating a q-axis voltage given value of the motor according to constraint conditions between the bus current command value and motor variables; based on Lyapunov stability theory, carrying out convergence judgment on the motor current under the q-axis given voltage, if the motor current is judged to be non-convergence, obtaining a motor q-axis current command value according to the approximate relation between a bus current command value and the motor q-axis current, and calculating a motor q-axis voltage given value based on a feedback linearization idea; and carrying out coordinate transformation on the given voltage of the d-q axes of the motor and outputting the voltage to the motor through the SVPWM module. The method has the advantages of high motor efficiency, high network side power factor, easy realization of control strategies and strong system robustness, and the network side power factor control effect is little influenced by system parameter errors.

Description

An electrolytic capacitor-free permanent magnet synchronous motor drive system based on bus current control Control Method

Technical field

The invention belongs to the field of motor control, and in particular relates to electrolytic capacitor-free permanent magnet synchronous motor drive system control technology.

Background technique

Permanent magnet synchronous motors are widely used in industry and home appliances due to their high efficiency and high power density. However, the DC bus electrolytic capacitors used in traditional AC-DC-AC permanent magnet synchronous motor variable frequency drive systems will reduce system reliability and worsen the grid-side input power factor. In order to meet the grid-side input power requirements, a power factor correction circuit needs to be added. Therefore, research on using film capacitors to replace bus electrolytic capacitors and using control strategies to improve grid-side input power factor has received widespread attention.

The currently existing electrolytic capacitor-free permanent magnet synchronous motor drive system control method uses repetitive controllers, proportional resonance controllers, etc. to control power and current to improve grid-side power factor. However, there are problems such as poor control effect and controller Problems such as difficulty in parameter tuning and low motor efficiency.

Contents of the invention

In order to solve the above technical problems, the present invention provides an electrolytic capacitor-free permanent magnet synchronous motor drive system control method based on bus current control, which directly controls the bus current based on system convergence analysis, has low system complexity, strong robustness, and can Achieving high power factor on the grid side and calculating the motor d-axis current command based on the minimum copper loss principle effectively improves motor efficiency.

The object of the present invention is to be achieved through the following technical solutions: a control method for a non-electrolytic capacitor permanent magnet synchronous motor drive system based on bus current control, which includes the following steps:

First, according to the bus current command value The constraints between the motor variables and the motor variables are used to obtain the motor q-axis voltage given value/>

Then based on Lyapunov stability theory, the q-axis voltage of the motor is given a given value Carry out convergence analysis on the motor current below; if it is judged to be convergent, the motor q-axis voltage given value/> If it is determined to be non-convergent, the bus current command value/> The approximate relationship with the motor q-axis current results in the motor q-axis current command value/> And based on the feedback linearization idea, the motor q-axis voltage given value/>

Finally, the motor d-axis voltage is given Q-axis voltage given/> Perform coordinate transformation to obtain the voltage given value in the stationary two-phase coordinate system/> Then output the voltage to the motor.

Further, the bus current command value Obtained according to the speed regulator output value, grid side voltage phase and bus capacitance value.

Further, the bus current command value The calculation method includes the following steps:

First, phase-lock the grid-side voltage waveform to obtain the grid-side voltage phase angle θ _s ;

Then, the difference between the motor speed command value and the actual speed is made, and then the grid-side input current command amplitude is output through the speed regulator. Combined with the grid-side voltage phase angle θ _s, the grid-side input current command instantaneous value/> Finally, input the instantaneous value of the current command on the grid side/> Subtract the instantaneous value of capacitor current i _c to obtain the bus current command value/>

Further, the d-axis current command value Calculated based on the minimum copper loss principle, the d-axis voltage given value/> obtained from the current regulator.

Further, the d-axis current command value is a constant. Since the q-axis current of the motor in the electrolytic capacitor-free drive system is a periodic sine wave, the d-axis current command constant value is obtained based on the minimum copper loss principle/> The calculation method includes the following steps:

First make the Lagrangian function in:

is the objective function, representing the system copper loss, where i _d is the motor d-axis current, i _qrms is the motor q-axis current effective value;/> is the system torque constraint condition, where L _d and L _q are the motor dq axis inductance respectively,/> is the motor permanent magnet flux linkage, i _qav is the average value of the motor q-axis current, and T is the average load torque of the motor; is the constraint condition between the effective value and the average value of the motor q-axis current; λ ₁ and λ ₂ are Lagrange multipliers;

Then let the first-order partial derivative of the Lagrangian function F(i _d ,i _qrms ,i _qav ,λ ₁ ,λ ₂ ) with respect to each variable equal to zero, we get:

Finally, the d-axis current i _d corresponding to the minimum copper loss control can be solved from the five equations in equation (1) and used as the d-axis command value. The expression is:

Further, obtain the given value of the motor q-axis voltage The method includes the following steps:

First, the inverter modulation ratio function in the stationary three-phase coordinate system is expressed as:

In the formula: A _m is the modulation ratio amplitude of the inverter, θ _e is the angle value of the motor d-axis leading the motor a-phase axis; It is the angle value of the inverter output phase angle leading the d-axis of the motor;

The motor voltage u _a , u _b , and u _c in the static three-phase coordinate system are expressed by the inverter transfer function F _d and the bus voltage u _dc as:

[u _a u _b u _c ] ^T ＝F _d ·u _dc (3);

Using the motor currents i _a , _ib , _ic and the inverter transfer function F _d in the static three-phase coordinate system, the bus current i _dc is expressed as:

i _dc = F _d ^T ·[i _a i _b i _c ] ^T (4);

After transforming equations (3) and (4) through the constant amplitude transformation from the stationary three-phase coordinate system to the rotating two-phase coordinate system, the motor voltage u _dq , bus current i _dc and inverter modulation ratio vector in the rotating coordinate system are obtained. The relationship between them is:

In the formula: I _m is the motor current amplitude; It is the angle value of the motor current phase angle leading the motor d-axis;/> is the motor current vector; A _d and A _q are the inverter modulation ratio vectors/> Component in the dq coordinate system;

Then a graph can be drawn according to equation (6), and the modulation ratio vector can be obtained from the graph In the motor current vector/> The calculation formula of the projection length L on is:

modulation ratio vector The coordinate values of the intersection points of the vertical line and the dq-axis coordinate system are:

Finally, the modulation ratio vector is obtained from equation (5) d-axis component/> According to the similar triangle relationship, we can get Then according to equation (5), the motor q-axis voltage given value/>

Further, the motor current convergence judgment method includes the following steps:

First, the voltage equations of the permanent magnet synchronous motor in the d-q coordinate system are expressed as:

In the formula: R is the stator resistance; ω _e is the electrical angular speed of the motor.

Then the calculated q-axis voltage of the motor is given Enter the motor voltage equation (9) and simplify it to:

According to the simplified relationship between the d-q axis current of the motor, the state variable equation of the q-axis current of the motor is:

Analyze the stability of the nonlinear equation shown in equation (11) based on Lyapunov direct method: Let is equal to zero, it can be found that the system has two equilibrium points, which are:

When the system is running normally, the motor q-axis current is positive, and it should be ensured that there is a positive balance point in the system, that is, the system needs to satisfy/> Take the positive equilibrium point i _{q_0} for convergence judgment:

For the convenience of analysis, y=i _q -i _{q_0} is brought into the above equation, so that the equilibrium point becomes the zero point of the state space, and the transformed equation is obtained:

Put equation (11) into equation (13) and simplify it:

Construct a positive definite Lyapunov function It is easy to get the derivative of Lyapunov function when y>-i _{q_0} is always less than zero, then the stable operation of the system can be ensured;

If the system does not satisfy With the two convergence conditions y>-i _{q_0} , the motor q-axis current command value is obtained from the approximate relationship between the motor q-axis current and the bus current/> Rewrite the motor q-axis voltage equation (9) as:/> According to the feedback linearization idea, let/> And bring it into the motor q-axis voltage equation and simplify it to get/> Reorder control rate/> Simplify/> where a is a positive constant,/> is the current error. It can be seen that the error between the current command and the actual current converges to zero over time.

Further, finally the motor d-axis voltage is given Q-axis voltage given/> Perform coordinate transformation to obtain the voltage given value in the stationary two-phase coordinate system/> The voltage is then output to the motor through the SVPWM module.

The beneficial effects of the present invention are: the present invention can be used in all electrolytic capacitor-free permanent magnet synchronous motor drive systems. Compared with the existing technology, the present invention obtains the d-axis current of the motor based on the principle of minimum copper loss, which improves the efficiency of the motor; directly calculates the given value of the q-axis voltage of the motor based on the constraints between the bus current command value and the motor variables, and can realize the network The power factor on the side is high, and the power factor control effect on the grid side is less affected by system parameter errors. The overall control strategy is easy to implement and the system is highly robust.

Description of the drawings

Figure 1 is a topological block diagram of an electrolytic capacitor-free drive system in an embodiment of the present invention;

Figure 2 is a block diagram of the inverter modulation ratio vector calculation in one embodiment of the present invention;

Figure 3 is a simulated d-q axis current waveform in an embodiment of the present invention;

Figure 4 is a simulated grid-side input current waveform in an embodiment of the present invention.

Detailed ways

The present invention will be described in detail below based on the accompanying drawings to make the purpose and effects of the present invention more apparent.

In one embodiment, a control method for an electrolytic capacitor-free permanent magnet synchronous motor drive system based on bus current control is provided, including the following steps:

First, according to the bus current command value The constraints between the motor variables and the motor variables are used to obtain the motor q-axis voltage given value/>

Then based on Lyapunov stability theory, the motor q-axis voltage is given a given value Carry out convergence analysis on the motor current below; if it is judged to be convergent, the motor q-axis voltage given value/> If it is judged as non-convergence, the bus current command value/> The approximate relationship with the motor q-axis current results in the motor q-axis current command value/> And based on the feedback linearization idea, the motor q-axis voltage given value/>

Finally, the motor d-axis voltage is given Q-axis voltage given/> Perform coordinate transformation to obtain the voltage given value in the stationary two-phase coordinate system/> Then output the voltage to the motor.

In one embodiment, the bus current command value Obtained according to the speed regulator output value, grid side voltage phase and bus capacitance value.

In one embodiment, the bus current command value The calculation method includes the following steps:

First, phase-lock the grid-side voltage waveform to obtain the grid-side voltage phase angle θ _s ;

Then, the difference between the motor speed command value and the actual speed is made, and then the grid-side input current command amplitude is output through the speed regulator. Combined with the grid-side voltage phase angle θ _s, the grid-side input current command instantaneous value/> Finally, input the instantaneous value of the current command on the grid side/> Subtract the instantaneous value of capacitor current i _c to obtain the bus current command value/>

In one embodiment, the d-axis current command value Calculated based on the minimum copper loss principle, d-axis voltage given value/> obtained from the current regulator.

Further, the d-axis current command value is a constant. Since the q-axis current of the motor in the electrolytic capacitor-free drive system is a periodic sine wave, the d-axis current command constant value is obtained based on the minimum copper loss principle/> The calculation method includes the following steps:

First make the Lagrangian function in:

is the objective function, representing the system copper loss, where i _d is the motor d-axis current, i _qrms is the motor q-axis current effective value;/> is the system torque constraint condition, where L _d and L _q are the motor dq axis inductance respectively,/> is the motor permanent magnet flux linkage, i _qav is the average value of the motor q-axis current, and T is the average load torque of the motor; is the constraint condition between the effective value and the average value of the motor q-axis current; λ ₁ and λ ₂ are Lagrange multipliers;

Then let the first-order partial derivative of the Lagrangian function F(i _d ,i _qrms ,i _qav ,λ ₁ ,λ ₂ ) with respect to each variable equal to zero, we get:

Finally, the d-axis current i _d corresponding to the minimum copper loss control can be solved from the five equations in equation (1) and used as the d-axis command value. The expression is:

In one embodiment, the motor q-axis voltage given value is obtained The method includes the following steps:

First, the inverter modulation ratio function in the stationary three-phase coordinate system is expressed as:

In the formula: A _m is the modulation ratio amplitude of the inverter, θ _e is the angle value of the motor d-axis leading the motor a-phase axis; It is the angle value of the inverter output phase angle leading the d-axis of the motor;

The motor voltage u _a , u _b , and u _c in the static three-phase coordinate system are expressed by the inverter transfer function F _d and the bus voltage u _dc as:

[u _a u _b u _c ] ^T = F _d · u _dc (3); The bus current i dc is represented by the motor currents i _a , _ib , _ic and the inverter transfer function F _d in the static three-phase coordinate _system . for:

i _dc = F _d ^T ·[i _a i _b i _c ] ^T (4);

After transforming equations (3) and (4) through the constant amplitude transformation from the stationary three-phase coordinate system to the rotating two-phase coordinate system, the motor voltage u _dq , bus current i _dc and inverter modulation ratio vector in the rotating coordinate system are obtained. The relationship between them is:

In the formula: I _m is the motor current amplitude; It is the angle value of the motor current phase angle leading the motor d-axis;/> is the motor current vector; A _d and A _q are the inverter modulation ratio vectors/> Component in the dq coordinate system;

Then according to equation (6), Figure 2 can be drawn, and the modulation ratio vector can be obtained from Figure 2 In the motor current vector/> The calculation formula of the projection length L on is:

modulation ratio vector The coordinate values of the intersection points of the vertical line and the dq-axis coordinate system are:

Finally, the modulation ratio vector is obtained from equation (5) d-axis component/> According to the similar triangle relationship, we can get Then according to equation (5), the motor q-axis voltage given value/>

In one embodiment, the motor current convergence judgment method includes the following steps:

First, the voltage equations of the permanent magnet synchronous motor in the d-q coordinate system are expressed as:

In the formula: R is the stator resistance; ω _e is the electrical angular speed of the motor.

Then the calculated q-axis voltage of the motor is given Enter the motor voltage equation (9) and simplify it to:

According to the simplified relationship between the d-q axis current of the motor, the state variable equation of the q-axis current of the motor is:

Analyze the stability of the nonlinear equation shown in equation (11) based on Lyapunov direct method: Let Equal to zero, it can be found that the system has two equilibrium points, which are:

When the system is running normally, the motor q-axis current is positive, and it should be ensured that there is a positive balance point in the system, that is, the system needs to satisfy/> Take the positive equilibrium point i _{q_0} for convergence judgment:

For the convenience of analysis, y=i _q -i _{q_0} is brought into the above equation, so that the equilibrium point becomes the zero point of the state space, and the transformed equation is obtained:

Put equation (11) into equation (13) and simplify it:

Construct a positive definite Lyapunov function It is easy to get the derivative of Lyapunov function when y>-i _{q_0} is always less than zero, then the stable operation of the system can be ensured;

If the system does not satisfy With the two convergence conditions y>-i _{q_0} , the motor q-axis current command value is obtained from the approximate relationship between the motor q-axis current and the bus current/> Rewrite the motor q-axis voltage equation (9) as:/> According to the feedback linearization idea, let/> And bring it into the motor q-axis voltage equation and simplify it to get/> Reorder control rate/> Simplify/> where a is a positive constant,/> is the current error. It can be seen that the error between the current command and the actual current converges to zero over time.

In one embodiment, finally the motor d-axis voltage is given Q-axis voltage given/> Perform coordinate transformation to obtain the voltage given value in the stationary two-phase coordinate system/> The voltage is then output to the motor through the SVPWM module.

During operation, the motor speed error is obtained by making the difference between the motor speed command value and the actual speed. The error value is passed through the motor speed regulator to obtain the grid-side input current command amplitude. Among them, the speed regulator can use a PI regulator.

Grid side input current command amplitude Combined with the grid-side voltage phase angle θ _s , the grid-side input current command instantaneous value is obtained Among them, the grid-side voltage phase angle θ _s can be obtained by using a second-order generalized integral phase-locked loop (SOGI-PLL). The specific calculation formula for the grid-side input current command amplitude is/>

As can be seen from Figure 1, the instantaneous value of the grid-side input current command Subtract the instantaneous value of capacitor current i _c to obtain the bus current command value/> Among them, the instantaneous value of the capacitor current/> In the formula, C _dc is the bus capacitance value; the bus current command value

By formula Get the motor d-axis current command value/> Among them, the average value of the motor q-axis current i _qav is obtained by averaging the sliding window filter:/> In the formula, N is the number of sampling times in one bus voltage cycle, and i _q (k) represents the q-axis current i _q sampled at the kth time.

The difference between the motor d-axis current command value and the actual current is used to obtain the d-axis voltage given value through the current regulator. Among them, the current regulator can use a PI regulator.

From the bus current command value Combined with the motor current amplitude I _m to obtain the modulation ratio vector/> In the motor current vector/> The projection length L on

The modulation ratio vector is obtained from the sine and cosine function relationship. The coordinate values of the intersection points of the vertical line and the dq-axis coordinate system are:/>

The given value is given by the motor d-axis voltage Get the modulation ratio vector/> d-axis component/>

The modulation ratio vector is obtained according to the similar triangle relationship shown in Figure 2 q-axis component/>

Finally, the modulation ratio vector q-axis component/> Combined with the bus voltage u _dc , we get the q-axis voltage given value/>

pass Two conditions with y>-i _{q_0} determine whether the motor current converges. If the two equations cannot be satisfied at the same time, the q-axis voltage given value needs to be changed/> The specific methods are:

The q-axis current command value is obtained from the relationship between the motor q-axis current and the bus current.

Obtain the q-axis voltage given value based on the feedback linearization idea

Give the motor d-axis voltage Q-axis voltage given/> Perform coordinate transformation to obtain the voltage given value in the stationary two-phase coordinate system/> Then the given voltage is output to the motor through the SVPWM module.

The invention can be used in all electrolytic capacitor-free permanent magnet synchronous motor drive systems. Compared with the existing technology, the present invention obtains the d-axis current of the motor based on the principle of minimum copper loss, which improves the efficiency of the motor; directly calculates the given value of the q-axis voltage of the motor based on the constraints between the bus current command value and the motor variables, and can realize the network The power factor on the side is high, and the power factor control effect on the grid side is less affected by system parameter errors. The overall control strategy is easy to implement and the system is highly robust. The power factor control effect is shown in Figures 3 and 4. In the q-axis current convergence area, the grid-side input current is a standard sine wave, thereby maximizing the grid-side power factor.

Claims (5)

1. The control method of the electrolytic capacitor-free permanent magnet synchronous motor driving system based on bus current control is characterized by comprising the following steps of:

firstly, according to the bus current command valueConstraint conditions between the motor variable and the motor q-axis voltage set value +.>

Then the motor q-axis voltage set value is set based on Lyapunov stability theoryCarrying out convergence analysis on the current of the motor; if convergence is determined, the motor q-axis voltage given value +.>If it is judged that the current is not converged, the current is judged to be +/based on the bus current command value>The approximate relation between the motor q-axis current and the motor q-axis current obtains the motor q-axis current command value +.>And based on feedback linearization concept, obtaining motor q-axis voltage given value +.>

Finally, the motor is arrangedd-axis voltage settingq-axis voltage is given>Performing coordinate transformation to obtain voltage given value +.>Outputting the voltage to the motor;

d-axis current command value of motorBased on minimum copper loss principle calculation, motor d-axis voltage given value +.>Obtained from a current regulator; d-axis current command value of motor->As the q-axis current of the motor of the electrolytic capacitor-free driving system is a periodic sine wave, the d-axis current instruction constant value of the motor is obtained based on the principle of minimum copper loss>The calculation method comprises the following steps:

first performing Lagrangian functionWherein:

as an objective function, the copper loss of the system is expressed, wherein i _d For motor d-axis current, i _qrms The q-axis current effective value of the motor; />As a constraint condition of system torque, L is _d ，L _q D-q axis inductances of the motors respectively, < >>I is the flux linkage of a permanent magnet of the motor _qav The average value of q-axis current of the motor is represented by T, and the average load torque of the motor is represented by T;the constraint condition between the effective value and the average value of the q-axis current of the motor is adopted; lambda (lambda) ₁ ，λ ₂ Is a Lagrangian multiplier;

then let Lagrangian function F (i _d ,i _qrms ,i _qav ,λ ₁ ,λ ₂ ) The first partial derivative for each variable is equal to zero, yielding:

finally, solving the d-axis current i corresponding to the minimum copper loss control by five equation sets in the formula (1) _d And takes the same as a d-axis command valueThe expression is:

obtaining the given value of the q-axis voltage of the motorThe method of (1) comprises the following steps:

firstly, the transfer function F of the inverter under a static three-phase coordinate system _d Expressed as:

wherein: a is that _m For the amplitude value of the modulation ratio of the inverter, theta _e Leading the angle value of the phase shaft of the motor a for the motor d-axis;the angle value of the d axis of the motor is advanced for the output phase angle of the inverter;

the motor voltage u under the static three-phase coordinate system _a 、u _b 、u _c By inverter transfer function F _d And bus voltage u _dc Expressed as:

[u _a u _b u _c ] ^T ＝F _d ·u _dc (3)；

using motor current i in a stationary three-phase coordinate system _a 、i _b 、i _c Transfer function with inverter F _d Bus current i _dc Expressed as:

i _dc ＝F _d ^T ·[i _a i _b i _c ] ^T (4)；

transforming the constant amplitude value of the equation (3) and the equation (4) from a static three-phase coordinate system to a rotating two-phase coordinate system to obtain the motor voltage u under the rotating coordinate system _d 、u _q Bus current i _dc Modulation ratio vector with inverterThe relation is as follows:

wherein: i _m The current vector amplitude value of the motor;leading the angle value of the d axis of the motor for the phase angle of the motor current; />Is a motor current vector; a is that _d 、A _q Respectively inverter modulation ratio vector->A component in the d-q coordinate system;

then, the modulation ratio vector is plotted according to the formula (6)In the motor current vector->The calculation formula of the projection length L is as follows:

modulation ratio vectorThe coordinate values of the intersection points of the vertical line and the d-q axis coordinate system are respectively as follows:

finally, obtaining the modulation ratio vector by the method (5)D-axis component>Obtained from similar triangle relationsObtaining the motor q-axis voltage set value according to the formula (5)>

2. The control method of the electrolytic capacitor-less permanent magnet synchronous motor driving system based on bus current control according to claim 1, wherein the bus current command value is as followsAnd obtaining according to the output value of the speed regulator, the network side voltage phase and the bus capacitance value.

3. The control method of the electrolytic capacitor-less permanent magnet synchronous motor driving system based on bus current control according to claim 2, wherein the bus current command value is as followsThe calculation method comprises the following steps: firstly, the network side voltage waveform is phase-locked to obtain the network side voltage phase angle theta _s ；

Then the motor rotating speed command value is differenced with the actual rotating speed, and the current command amplitude is input from the output net side of the speed regulatorCombining net side voltage phase angle theta _s Obtaining the instantaneous value of the network side input current command +.>

Finally, inputting current command instantaneous value to network sideSubtracting the instantaneous value i of the capacitive current _c Obtaining bus current command value +.>

4. The control method of the electrolytic capacitor-less permanent magnet synchronous motor driving system based on bus current control according to claim 1, wherein the motor current convergence judging method comprises the steps of: firstly, respectively representing the voltage equation of the permanent magnet synchronous motor under a d-q coordinate system as follows:

wherein: r is stator resistance; omega _e Is the electrical angular velocity of the motor;

then giving the calculated motor q-axis voltageBringing a motor voltage equation (9), and simplifying to obtain:

simplifying the relation of the current of the motor d-q axis to obtain a state variable equation of the current of the motor q axis, wherein the state variable equation is as follows:

nonlinear equation stability represented by formula (11) is analyzed based on the lyapunov direct method: order theEqual to zero, two balance points exist in the system, and the two balance points are respectively:

when the system is in normal operation, the q-axis current of the motor is positive, and the positive balance point of the system is ensured, namely the system needs to meet +.>Taking positive balance point i _{q_0} And (3) performing convergence judgment:

for ease of analysis, y=i _q -i _{q_0} Bringing the equation into the state space zero point of the balance point to obtain a transformed equation:

combining the formula (11) with the formula (13) to simplify the process:

construction of a positive-going Lyapunov functionEasy-to-get y > -i _{q_0} Derivative of Lyapunov function +.>The constant value is smaller than zero, so that the stable operation of the system can be ensured;

if the system does not meetAnd y > -i _{q_0} Under these two convergence conditions, the motor q-axis current command value +_is obtained from the approximate relationship between the motor q-axis current and the bus current>The motor q-axis voltage equation (9) is rewritten as: />According to the feedback linearization idea, let ∈ ->And brings the motor q-axis voltage equation into the motor q-axis voltage equation, so as to simplify +.>Let control rate->Reduced->Wherein a is a positive constant, < >>As a current error, the error between the current command and the actual current converges to zero over time.

5. The control method of a permanent magnet synchronous motor driving system without electrolytic capacitor based on bus current control according to claim 1, wherein finally, the d-axis voltage of the motor is givenq-axis voltage is given>Performing coordinate transformation to obtain voltage given value +.>And then the SVPWM module outputs the voltage to the motor.